Migration of Monsoons Created, Then Killed Harappan Civilization

from the Los Angeles Times (Registration Required)

The slow eastward migration of monsoons across the Asian continent initially supported the formation of the Harappan civilization in the Indus valley by allowing production of large agricultural surpluses, then decimated the civilization as water supplies for farming dried up, researchers reported Monday. The results provide the first good explanation for why the Indus valley flourished for two millennia, sprouting large cities and an empire the size of contemporary Egypt and Mesopotamia combined, then dwindled away to small villages and isolated farms.

The Harappan civilization, named after its largest city, Harappa along the upper Indus River, evolved beginning about 5,200 years ago and reached its height between 4,500 and 3,900 years ago, stretching across what is now Pakistan, northwest India and Eastern Afghanistan. An urban society with large cities, a distinctive style of writing and extensive trade that reached as far as Mesopotamia, the society accounted for about 10% of the Earth's population at its height and rivaled Egypt in its power. Unlike Egypt and Mesopotamia, however, the Harappans did not attempt to develop irrigation to support agriculture. Instead, they relied on the annual monsoons, which allowed the accumulation of large agricultural surpluses--which, in turn, allowed the creation of cities. The civilization was largely forgotten by history until the 1920s, when researchers finally began studying it in depth.

The new research was performed by a team led by geologist Liviu Giosan of the Woods Hole Oceanographic Institution in Woods Hole, Mass., and published in the Proceedings of the National Academy of Science. Working in Pakistan, they used photographs taken by shuttle astronauts and images from the Shuttle Radar Topography Mission to prepare maps of land forms in the region, then verified them on the ground using drilling, coring and manually dug trenches.